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GRASS 8 Programmer's Manual 8.6.0dev(2026)-f6f2c534ea
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GIS Library - Geodesic distance routines. More...

Go to the source code of this file.
Functions | |
| void | G_begin_geodesic_distance (double a, double e2) |
| Begin geodesic distance. | |
| void | G_set_geodesic_distance_lat1 (double lat1) |
| Sets geodesic distance lat1. | |
| void | G_set_geodesic_distance_lat2 (double lat2) |
| Sets geodesic distance lat2. | |
| double | G_geodesic_distance_lon_to_lon (double lon1, double lon2) |
| Calculates geodesic distance. | |
| double | G_geodesic_distance (double lon1, double lat1, double lon2, double lat2) |
| Calculates geodesic distance. | |
GIS Library - Geodesic distance routines.
Distance from point to point along a geodesic code from Paul D. Thomas, 1970 "Spheroidal Geodesics, Reference Systems, and Local Geometry" U.S. Naval Oceanographic Office, p. 162 Engineering Library 526.3 T36s http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0703541
WARNING: this code is preliminary and may be changed, including calling sequences to any of the functions defined here.
(C) 2001-2009 by the GRASS Development Team
This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.
Definition in file geodist.c.
Begin geodesic distance.
Initializes the distance calculations for the ellipsoid with semi-major axis a (in meters) and ellipsoid eccentricity squared e2. It is used only for the latitude-longitude projection.
Note: Must be called once to establish the ellipsoid.
| a | semi-major axis in meters |
| e2 | ellipsoid eccentricity |
Definition at line 49 of file geodist.c.
Referenced by G_begin_distance_calculations().
Calculates geodesic distance.
Calculates the geodesic distance from lon1,lat1 to lon2,lat2 in meters.
Note: The calculation of the geodesic distance is fairly costly.
| [in] | lon1,lat1 | longitude,latitude of first point |
| [in] | lon2,lat2 | longitude,latitude of second point |
Definition at line 193 of file geodist.c.
References G_geodesic_distance_lon_to_lon(), G_set_geodesic_distance_lat1(), and G_set_geodesic_distance_lat2().
Referenced by G_distance(), and Vect_line_geodesic_length().
Calculates geodesic distance.
Calculates the geodesic distance from lon1,lat1 to lon2,lat2 in meters where lat1 was the latitude passed to G_set_geodesic_distance_latl() and lat2 was the latitude passed to G_set_geodesic_distance_lat2().
| [in] | lon1 | first longitude |
| [in] | lon2 | second longitude |
Definition at line 119 of file geodist.c.
References M_PI, Radians, t, and x.
Referenced by G_geodesic_distance().
Sets geodesic distance lat1.
Set the first latitude.
Note: Must be called first.
| [in] | lat1 | first latitude |
Definition at line 67 of file geodist.c.
References Radians.
Referenced by G_geodesic_distance().